JP2017169156A - Transimpedance amplifier and optical signal receiver - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a TIA capable of outputting a differential signal of good symmetry and free from phase shift with equal amplitude, and capable of linear operation with high gain, and to provide an optical signal receiver using the same.SOLUTION: A transimpedance amplifier 20 receives a current signal Iin outputted from a light-receiving element 1 by a current voltage conversion circuit 21, converts into a single-phase voltage signal Vin proportional to the current signal Iin, and gives it to a phase division circuit 22 consisting of a bipolar or field effect transistor. The phase division circuit 22 receives the inputted voltage signal Vin by the base (first terminal) of the transistor, for example, and outputs two-phase voltage signals Va(-), Vb(+) of inverted phase from the collector (second terminal) side and emitter (third terminal) side. A level matching circuit 23 receives the two-phase voltage signals Va(-), Vb(+), and converts into two-phase voltage signals Va(-)', Vb(+)' combining the average potentials, before being inputted to a differential amplifier circuit 24.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a transimpedance amplifier and an optical signal receiving apparatus that receive a current signal output from a photoelectric conversion element, convert it into a single-phase voltage signal, convert it into a differential signal whose phases are inverted, and output the differential signal. It relates to technology for improving performance.

  An optical signal receiving device that constitutes a receiving unit of an optical communication device receives an intensity-modulated optical signal by a photoelectric conversion element such as a photodiode, and a signal whose current value changes according to the intensity of input light from the photoelectric conversion element (Current signal) is converted into a single-phase voltage signal, and the single-phase voltage signal is reversed in phase so that it can be easily connected to subsequent differential processing circuits and transmission lines. It is converted into a voltage signal and output.

  A circuit having this current-voltage conversion function and a conversion output function into a two-phase voltage signal is generally called a transimpedance amplifier (hereinafter referred to as TIA).

An example of a conventional configuration of TIA is shown in FIG.
This TIA receives a current signal Iin output from a photoelectric conversion element such as a photodiode by a current-voltage conversion circuit (hereinafter referred to as an IV circuit) 11 and generates a voltage proportional to the magnitude of the current signal Iin. Is converted into a single-phase voltage signal Vin.

Here, the IV circuit 11 is configured to feed back the output signal of the inverting amplifier 11a to the input terminal via the feedback resistor R, and the resistance value of the feedback resistor R is greater than the input impedance of the amplifier 11a. If it is sufficiently high, the voltage signal Vin is approximately expressed as:
Vin = −Iin · R

  This single-phase voltage signal Vin is input to one input terminal of the differential amplifier circuit 12, and a DC reference voltage Vref is input to the other input terminal, so that two output terminals of the differential amplifier circuit 12 Voltage signals Vout (+) and Vout (−) having a magnitude almost proportional to the differential input (Vin−Vref) and having phases inverted from each other can be output.

  Here, if there is a difference between the average potential of the voltage signal Vin and the reference voltage Vref, the difference between the DC components is amplified, so that the operating point of the pair of differential transistors constituting the differential amplifier circuit 12 is from a normal region. As a result, the output signal is reduced in amplitude and distorted.

  Therefore, in this circuit example, the low-pass filter (LPF) 13 extracts the average potential Vave, which is a DC component of the voltage signal Vin, and inputs this to the differential amplifier circuit 12 as the reference voltage Vref.

  The TIA having the above configuration is disclosed in, for example, Patent Document 1. In this Patent Document 1, the current-voltage conversion circuit is called a “transimpedance amplifier”, and the entire circuit including the differential amplifier circuit is an optical signal receiving circuit. The entire circuit including the amplifier circuit will be referred to as TIA.

JP 2007-243510 A

  In the conventional TIA described above, a single-phase voltage signal Vin is input to one input terminal of the differential amplifier circuit 12, and a DC voltage Vref equal to the average potential of the voltage signal Vin is input to the other input terminal to amplify the signal. Therefore, the operations of the pair of differential transistors constituting the differential amplifier circuit 12 are not completely symmetric. Depending on the circuit configuration, the amplitudes of the output voltage signals Vout (+) and Vout (−) Are not equal.

  That is, the differential amplifier circuit 12 generally includes load resistors R1 and R2 having the same resistance value between the collectors of the pair of differential transistors Tr1 and Tr2 and the power source Vcc on the high potential side, as shown in FIG. The emitters are connected to each other through resistors R3 and R4 having the same resistance value, and the connection point is connected to a power source on the low potential side through a common resistor R5 (or constant current source). In addition, by giving the signals IN (+) and IN (-) to the bases of the transistors Tr1 and Tr2, two signals of opposite phase and in-phase are proportional to the difference signal [IN (+)-IN (-)]. Vout (+) and Vout (-) are output.

  Here, when a single-phase voltage signal Vin is input to one input terminal of the differential amplifier circuit and a DC voltage Vref equal to the average potential of Vin is input to the other input terminal, the current source of the differential amplifier circuit is In the case of an ideal constant current source, the two transistors Tr1 and Tr2 amplify almost symmetrically and the amplitudes of the output signals Vout (+) and Vout (−) are substantially equal.

  On the other hand, as shown in Patent Document 1, in order to obtain a high dynamic range with a low power supply voltage, a configuration using a resistor as a current source of a differential amplifier circuit as shown in FIG. 9 is effective. When a single-phase voltage signal Vin is input to one input terminal and a DC voltage Vref equal to the average potential of Vin is input to the other input terminal, the output signal Vout (+) , The amplitude of Vout (−) is different.

  That is, in the differential amplifier circuit in which the current source is configured by a resistor, a sufficient constant current operation is not performed. Therefore, the common-mode gain of the differential amplifier circuit is not suppressed, and the current flowing through the current source resistor depends on the state of the voltage signal Vin. Therefore, when Vin is high, the current of the current source resistance increases, and when Vin is low, the current of the current source resistance decreases. This acts to emphasize the amplitude change of the output signal Vout (+), causing an asymmetry in which the amplitude of Vout (+) is larger than the amplitude of Vout (−), which causes signal distortion.

  In Patent Document 1, the constant current source of the differential amplifier circuit is replaced with a resistor in order to maximize the amplitude of the voltage signal output from the current-voltage conversion circuit using a single power supply of about 3 volts. As a means to improve the asymmetry of the output waveform, the output of this differential amplifier circuit is limited by another differential amplifier circuit to shape the waveform, but multi-level modulation such as pulse amplitude modulation is used. In optical communication, TIA is required to have a function of linearly amplifying a signal, and thus the above-mentioned means cannot be applied to TIA for the above application.

  Even when the current source of the differential amplifier circuit is an ideal constant current source, a single-phase voltage signal Vin is input to one input terminal of the differential amplifier circuit, and Vin is input to the other input terminal. In the configuration in which the signal voltage is amplified by inputting the DC voltage Vref equal to the average potential, the operation of the pair of differential transistors constituting the differential amplifier circuit is not completely symmetric. Deviation occurred, causing signal quality degradation.

  Further, in the above-described conventional TIA, a single-phase voltage signal Vin is input to one input terminal of the differential amplifier circuit 12, and a DC voltage Vref equal to the average potential of the voltage signal Vin is input to the other input terminal. Since it is configured to input and amplify the signal, a high gain cannot be obtained compared to the TIA configured to input differential signals whose phases are inverted to the two input terminals of the differential amplifier circuit 12, and the S of the receiving unit. / N ratio could not be increased.

  The present invention solves the above-described problem, and provides a TIA having a high gain and capable of outputting a differential signal with equal amplitude and no phase shift, capable of linear operation, and an optical signal receiving apparatus using the TIA. The purpose is to do.

In order to achieve the above object, the transimpedance amplifier according to claim 1 of the present invention comprises:
A current-voltage conversion circuit (21) for converting an input current signal into a single-phase voltage signal;
A phase for receiving a single-phase voltage signal output from the current-voltage conversion circuit at the first terminal of the transistor, and outputting a two-phase voltage signal whose phases are inverted from the second terminal side and the third terminal side of the transistor A dividing circuit (22);
A level adjusting circuit (23) for receiving a two-phase voltage signal output from the phase dividing circuit and outputting the average potential of the two-phase voltage signal;
One of the two-phase voltage signals whose average potentials are matched by the level matching circuit is received by the inverting input terminal and the other is received by the non-inverting input terminal, and the differential component of the two-phase voltage signals input to the two input terminals is amplified. And a differential amplifier circuit (24) for outputting the amplified signal from the inverted output terminal and the non-inverted output terminal as signals whose phases are inverted from each other.

The transimpedance amplifier according to claim 2 of the present invention is the transimpedance amplifier according to claim 1,
The transistor constituting the phase dividing circuit is a bipolar transistor in which the first terminal is a base, the second terminal is a collector, the third terminal is an emitter, or the first terminal is a gate, and the second terminal is a drain. The third terminal is any one of a source field effect transistor.

The transimpedance amplifier according to claim 3 of the present invention is the transimpedance amplifier according to claim 1 or 2,
The level adjusting circuit includes:
A level shift circuit (23a) for reducing an average potential of a voltage signal output from the second terminal side of the transistor of the phase dividing circuit by a predetermined voltage using a forward voltage drop of the transistor or the diode; It is characterized by being.

A transimpedance amplifier according to claim 4 of the present invention is the transimpedance amplifier according to any one of claims 1 to 3,
The level adjusting circuit includes:
A level shift circuit (23b) for increasing an average potential of a voltage signal output from the third terminal side of the transistor of the phase dividing circuit by a predetermined voltage using a forward voltage drop of the transistor or the diode; It is characterized by being.

A transimpedance amplifier according to claim 5 of the present invention is the transimpedance amplifier according to any one of claims 1 to 4.
The level adjusting circuit includes:
An error compensation voltage generator (23c) that generates an error compensation voltage that can be varied by a manual operation, and the error compensation voltage is used as at least one of two-phase voltage signals output from the phase division circuit, or The error of the average potential of the two-phase voltage signal is reduced by being superimposed on at least one of the two-phase voltage signals input to the differential amplifier circuit.

A transimpedance amplifier according to claim 6 of the present invention is the transimpedance amplifier according to any one of claims 1 to 4.
The level adjusting circuit includes:
The difference between the average potentials of the two-phase voltage signals input to the differential amplifier circuit or the difference between the average potentials of the two-phase voltage signals output from the differential amplifier circuit is detected, and the difference is reduced. And an error voltage detection circuit (23e) for obtaining an error compensation voltage necessary for this, and the error compensation voltage is input to at least one of the two-phase voltage signals output from the phase dividing circuit or the differential amplifier circuit. The difference between the average potentials is reduced by being superimposed on at least one of the two-phase voltage signals.

An optical signal receiving apparatus according to claim 7 of the present invention is
A photoelectric conversion element (1) that receives an optical signal and outputs a current signal;
In an optical signal receiving device having a transimpedance amplifier (20) for receiving a current signal output from the photoelectric conversion element,
The transimpedance amplifier is the transimpedance amplifier according to any one of claims 1 to 6.

  Thus, in the TIA of the present invention, the single-phase voltage signal output from the current-voltage conversion circuit is applied to the first terminal of the transistor of the phase dividing circuit, and the phases are inverted from each other from the second terminal side and the third terminal side. The two-phase voltage signals are output, and the average potential of the two-phase voltage signals is adjusted by the level adjusting circuit and then applied to the differential amplifier circuit.

  For this reason, the differential amplifier circuit receives the voltage signals having the average potentials equal to each other and the phases of which are inverted. Therefore, the differential amplifier circuit has a symmetrical two-phase voltage signal having the same amplitude. Since it can be obtained by gain and there is no need to limit the signal for waveform shaping as in the prior art, a linearly operable TIA can be realized.

  Further, by applying the present invention to the TIA of the optical signal receiving apparatus, it is possible to receive at a high S / N ratio even when attenuation in the transmission path of the optical signal input to the photoelectric conversion element is large, and long distance Optical communication is possible.

Configuration diagram of an embodiment of the present invention The figure which shows the circuit example of the principal part of embodiment of this invention The figure which shows the circuit example of the principal part of embodiment of this invention The figure which shows another circuit example of the principal part of embodiment of this invention The figure which shows another circuit example of the principal part of embodiment of this invention The figure which shows the characteristic of embodiment of this invention and a conventional circuit The figure which shows the characteristic of embodiment of this invention and a conventional circuit Diagram showing a conventional circuit The figure which shows the circuit example of the differential amplifier circuit

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 shows a configuration of an optical signal receiving apparatus including a TIA 20 and a photoelectric conversion element 1 to which the present invention is applied.

  In FIG. 1, a current-voltage conversion circuit 21 converts an input current signal Iin into a single-phase voltage signal Vin, and basically feeds back between an input terminal and an output terminal of an inverting amplifier 21a. The resistor R is connected, operates so that a current equal to the input current signal Iin flows from the output terminal to the input terminal, and outputs a single-phase voltage signal Vin equal to −Iin · R from the output terminal. .

  This single-phase voltage signal Vin is input to the phase division circuit 22. The phase division circuit 22 converts the input single-phase voltage signal Vin into two-phase voltage signals Va (−) and Vb (+) whose phases are inverted from each other.

  The phase dividing circuit 22 can be configured using a bipolar transistor or a field effect transistor (FET). FIG. 2 shows a circuit example using a bipolar transistor.

  The circuit in FIG. 2A has a configuration in which the voltage signal Vin is applied to the base (first terminal) of the transistor Tr11, and resistors R11 and R12 are connected to the collector (second terminal) and the emitter (third terminal). A voltage signal Va (−) whose phase is inverted with respect to the voltage signal Vin is output from the collector side, and a voltage signal Vb (+) in phase with the voltage signal Vin is output from the emitter side.

  Further, instead of the transistor Tr1 in FIG. 2A, a configuration using a cascode circuit including two transistors Tr12 and Tr13 as shown in FIG. 2B is possible. In this configuration, a transistor Tr13 that forms a grounded base type amplifier circuit is connected between the collector (second terminal) of the transistor Tr12 that receives the voltage signal Vin at the base (first terminal) and the load resistor R11. A bias voltage Vbb is applied to the base of the transistor Tr13. In the case of this circuit, the voltage signal Vin is received at the base (first terminal) of the transistor Tr12, and the voltage signal Vin from the collector side of the transistor Tr13 connected to the transistor Tr12 and the emitter (third terminal) side of the transistor Tr12. Outputs a signal in phase with the opposite phase.

  In this way, when the phase division circuit 22 using transistors generates voltage signals whose phases are inverted, a difference occurs in the average potential of the two-phase output voltage signals Va (−) and Vb (+). For example, in the configuration of FIG. 2A, there is usually a potential difference ΔV of about 1 to 2 volts between the collector voltage and the emitter voltage of the transistor Tr11 in the normal operating range. Appears as a difference between the average potentials of the voltage signals Va (-) and Vb (+). When the voltage signals Va (−) and Vb (+) having the potential difference ΔV are applied to the differential amplifier circuit 24 described later as they are, the potential difference ΔV is also amplified and output after being amplified. Therefore, in a power supply of about 3 V that is generally used in an optical communication device, the operating points of the pair of differential transistors constituting the differential amplifier circuit 24 become unbalanced and deviate from the normal region, and the output signal As a result, the amplitude is reduced or distorted.

  Therefore, in this embodiment, the two-phase voltage signals Va (−) and Vb (+) output from the phase dividing circuit 22 are received, and the average potentials of the voltage signals Va (−) and Vb (+) are adjusted. Level output circuit 23 for outputting the output.

  As the level adjusting circuit 23, various methods can be considered. As one method, the voltage signal having the higher average potential (Va (−) in the above circuit example) of the two-phase voltage signals Va (−) and Vb (+) is output by the first level shift circuit 23a. For example, the voltage signal having a lower average potential (Vb (+) in the above circuit example) is shifted to the higher side by ΔV / 2 by the second level shift circuit 23b. A difference ΔV between the average potentials of the two voltage signals Va (−) and Vb (+) is made substantially zero and output.

  More specifically, as shown in FIG. 3, the first shift circuit 23a is formed by an emitter follower circuit using a transistor Tr21 and an emitter resistor R21, and a voltage signal Va (−) is applied to the base of the transistor Tr21. A voltage signal Va (−) ′ shifted to the lower side by the voltage drop (≈ΔV / 2) between the base and emitter of the transistor Tr21 is output from the emitter. It is also possible to connect a diode instead of the transistor Tr21 of this emitter follower circuit, apply the voltage signal Va (−) to the anode side, and output it by shifting it to the lower side by the forward voltage drop of the diode.

  The second shift circuit 23b includes a diode D21 and a resistor R22 connected between the anode side of the diode D21 and the power source Vcc on the high potential side. The voltage signal Vb is connected to the cathode side of the diode D21. (+) Is given, and the voltage signal Vb (+) ′ shifted to the higher side by the forward voltage drop (≈ΔV / 2) of the diode D21 is outputted from the anode side.

  As described above, of the two-phase voltage signals, the higher average potential is shifted lower, the lower average potential is shifted higher, and the average potential of the two voltage signals is added to the inverting input of the differential amplifier circuit 24. By inputting to the terminal and the non-inverting input terminal, the operating points of the pair of differential transistors constituting the differential amplifier circuit 24 can be balanced.

  It should be noted that only the voltage signal having the higher average potential (Va (-) in the above circuit example) is shifted by approximately ΔV to match the voltage signal having the lower average potential. It is also possible to adopt a method in which only the lower voltage signal (Vb (+) in the above circuit example) is shifted upward by approximately ΔV and matched with the voltage signal Va (−) having the higher average potential. In the case of adopting these methods, the voltage shift by the transistors and diodes of the first shift circuit 23a and the second shift circuit 23b may be a two-stage configuration.

  In the above embodiment, the case where the voltage to be shifted is fixed as the level adjusting circuit has been described. However, when the average potential of the two-phase voltage signal is to be adjusted more precisely, for example, as shown in FIG. An error compensation voltage generator 23c capable of varying the voltage is provided, and the error compensation voltage E is supplied to at least the voltage signals Va (−) and Vb (+) via an error voltage application circuit 23d composed of a resistance coupling circuit or the like. On the other hand, it is superposed (added or subtracted) on at least one of the voltage signals Va (−) ′ and Vb (+) ′. Thus, the average potential of the two-phase voltage signal input to the differential amplifier circuit 24 or the two-phase voltage signal output from the differential amplifier circuit 24 can be accurately matched.

  Further, as shown in FIG. 5, an error voltage detection circuit 23e that automatically detects an error voltage of the average potential is provided, and the error compensation voltage E and the error compensation voltage application circuit 23d are reduced so as to reduce the detected error voltage. Is superimposed on at least one of the voltage signals Va (−) and Vb (+) or at least one of the voltage signals Va (−) ′ and Vb (+) ′ through the input signal to be input to the differential amplifier circuit 24. The average potential of the voltage signal or the average potential of the voltage signal output from the differential amplifier circuit 24 can be automatically adjusted with high accuracy.

  FIG. 5A is a circuit example in which the average potential of the voltage signal input to the differential amplifier circuit 24 is automatically adjusted. The error voltage detection circuit 23e of this circuit example is a voltage signal Va (−) ′. , Vb (+) ′ is detected, an error compensation voltage E necessary for reducing the difference is obtained, and an error compensation voltage application circuit provided on the input side of the first shift circuit 23a is obtained. It is superimposed on the voltage signal Va (−) via 23d.

  FIG. 5B is an example of a circuit that automatically adjusts the average potential of the voltage signal output from the differential amplifier circuit 24. The error voltage detection circuit 23e of this circuit example is the differential amplifier circuit 24. The error compensation voltage E required for detecting the difference E ′ of the average potential of the voltage signal output from the signal and reducing the difference is obtained by using the differential gain A of the differential amplifier circuit 24. It is obtained by calculation and superimposed on the voltage signal Va (−) via an error compensation voltage application circuit 23d provided on the input side of the first shift circuit 23a.

  In the above circuit example, the difference between the average potentials of the voltage signals of the two phases is detected, the error compensation voltage E required to reduce the difference is obtained, and input to the preceding circuit from the detection position of the difference between the average potentials. The signal is superimposed on one of the two-phase signals, but may be superimposed via the error compensation voltage application circuit 23d inserted in the signal line at the detection position. Further, not only one of the two-phase signals but also an error compensation voltage may be superimposed on both to reduce the difference in average potential. Further, as a modification when detecting the error voltage of the two-phase voltage signal output from the differential amplifier circuit 24 as shown in FIG. 5B, when the differential amplifier circuit 24 has a multi-stage configuration, either The error voltage can also be detected from the output of this stage.

  If the above configuration is used, voltage signals Va (−) ′ and Vb (+) ′ whose phases are mutually inverted and whose average potentials are always matched by automatic control can be input to the differential amplifier circuit 24.

  Further, if R11 and R12 of the phase division circuit of FIG. 2 are set to the same resistance value, the amplitudes of Va (−) and Vb (+) can be made substantially equal, and the phase is reversed in the differential amplifier circuit 24. Since the voltage signal with the same amplitude and average potential can be input, the operation of the differential amplifier circuit is the most symmetric, and the output signal Vout with the same amplitude is obtained even when the current source is composed of resistors. (+) And Vout (-) can be obtained.

  Further, since the differential amplifier circuit 24 amplifies the difference between the input signals Va (−) ′ and Vb (+) ′ whose phases are inverted from each other with the differential gain A, the single-phase voltage signal Vin is amplified by the differential amplifier circuit. An output signal having a larger amplitude than the conventional configuration to be amplified can be obtained. Thereby, the gain of the entire TIA can be increased.

  FIG. 6 shows a simulation result of frequency characteristics of transimpedance gain (dBohm) at two output terminals (Vout (+), Vout (−)) of the conventional circuit and the circuit according to the embodiment of the present invention. In both circuits, the power supply voltage is 3.3 V, and the current source of the differential amplifier circuit is constituted by a resistor. Further, the automatic control circuit of FIG. 5A is used for the circuit of the embodiment of the present invention, and the resistance values of R11 and R12 of the phase division circuit are both 50Ω. InP HBT with ft: 230 GHz and fmax: 400 GHz is used as a transistor forming the circuit. The frequency to be analyzed was set to 100 kHz to 50 GHz in a frequency region generally used in optical communication.

  As shown in FIG. 6B, in the conventional circuit, a difference of about 3 dB occurs in the gain of the two output signals from the low frequency region. As described above, since a single-phase voltage signal is input to one input terminal of the differential amplifier circuit in which the current source is a resistor, the signal is amplified. This is because the current of the amplifier circuit changes and the operation of the circuit becomes asymmetric.

  On the other hand, in the circuit according to the embodiment of the present invention shown in FIG. 6A, voltage signals having the same amplitude, whose phases are inverted from each other, are input to the two input terminals of the differential amplifier circuit. Even in the differential amplifier circuit, the circuit operates with good symmetry, and the gains of the two output signals have substantially the same characteristics.

  FIG. 7 shows the transimpedance gain (dBohm) and its phase characteristics when the current source of the differential amplifier circuit is replaced with an ideal constant current source in the conventional circuit of FIG. 6 and the circuit of the embodiment of the present invention. Simulation results are shown. The phase of Vout (−) indicates a phase shifted by 180 degrees.

  Looking at the gain of the conventional circuit in FIG. 7B, the gains of the two output signals in the low frequency region are equal because the current source of the differential amplifier circuit is an ideal constant current source. However, a gain difference appears from 30 GHz or more, and the difference at 50 GHz is 1.5 dB. In addition, the phase characteristics of the two output signals have a phase shift of 17 degrees at 50 GHz. This phase shift becomes a factor such as jitter deterioration of the subsequent circuit. On the other hand, in the circuit according to the embodiment of the present invention, as shown in FIG. 7A, the gains and phases of the two output signals have the same characteristics in all frequency regions. Further, when the gain of the circuit of the embodiment of the present invention is compared with the gain of the conventional circuit, the gain of the circuit of the embodiment of the present invention is about 4 dB higher than that of the conventional circuit although the cut-off frequency Fc is almost equal. Yes.

  From the above, it can be seen that the circuit according to the embodiment of the present invention can output a differential signal with equal amplitude and no phase shift, and a high gain.

  In the above embodiment, an example in which a bipolar transistor is used as the transistor constituting the phase division circuit 22 is shown. However, the transistors Tr11 to Tr13 in the circuit shown in FIG. 2 are replaced with field effect transistors (FETs). It is also possible. In this case, the bases, collectors, and emitters of the transistors Tr11 to Tr13 may be replaced with FET gates, drains, and sources, respectively. The gates, drains, and sources corresponding to the bases, collectors, and emitters of the transistors Tr11, Tr12 The first terminal, the second terminal, and the third terminal may be used respectively. Further, the current-voltage conversion circuit 21 and the differential amplifier circuit 24 may be configured not only with a bipolar transistor but also with a field effect transistor (FET).

  DESCRIPTION OF SYMBOLS 1 ... Photoelectric conversion element, 20 ... TIA (transimpedance amplifier), 21 ... Current-voltage conversion circuit, 22 ... Phase division circuit, 23 ... Level adjustment circuit, 23a ... 1st shift circuit, 23b ... ... Second shift circuit, 23c... Error compensation voltage generator, 23d... Error compensation voltage application circuit, 23e... Error voltage detection circuit, 24.

Claims (7)

A current-voltage conversion circuit (21) for converting an input current signal into a single-phase voltage signal;
A phase for receiving a single-phase voltage signal output from the current-voltage conversion circuit at the first terminal of the transistor, and outputting a two-phase voltage signal whose phases are inverted from the second terminal side and the third terminal side of the transistor A dividing circuit (22);
A level adjusting circuit (23) for receiving a two-phase voltage signal output from the phase dividing circuit and outputting the average potential of the two-phase voltage signal;
One of the two-phase voltage signals whose average potentials are matched by the level matching circuit is received by the inverting input terminal and the other is received by the non-inverting input terminal, and the differential component of the two-phase voltage signals input to the two input terminals is amplified. And a differential amplifier circuit (24) for outputting the amplified signal from the inverting output terminal and the non-inverting output terminal as a signal whose phases are inverted from each other.   The transistor constituting the phase dividing circuit is a bipolar transistor in which the first terminal is a base, the second terminal is a collector, the third terminal is an emitter, or the first terminal is a gate, and the second terminal is a drain. 2. The transimpedance amplifier according to claim 1, wherein the third terminal is one of a source field effect transistor. The level adjusting circuit includes:
A level shift circuit (23a) for reducing an average potential of a voltage signal output from the second terminal side of the transistor of the phase dividing circuit by a predetermined voltage using a forward voltage drop of the transistor or the diode; The transimpedance amplifier according to claim 1, wherein the transimpedance amplifier is provided. The level adjusting circuit includes:
A level shift circuit (23b) for increasing an average potential of a voltage signal output from the third terminal side of the transistor of the phase dividing circuit by a predetermined voltage using a forward voltage drop of the transistor or the diode; The transimpedance amplifier according to claim 1, wherein the transimpedance amplifier is provided. The level adjusting circuit includes:
An error compensation voltage generator (23c) that generates an error compensation voltage that can be varied by a manual operation, and the error compensation voltage is used as at least one of two-phase voltage signals output from the phase division circuit, or 5. The error of the average potential of the two-phase voltage signal is reduced by superimposing it on at least one of the two-phase voltage signals input to the differential amplifier circuit. The transimpedance amplifier described. The level adjusting circuit includes:
The difference between the average potentials of the two-phase voltage signals input to the differential amplifier circuit or the difference between the average potentials of the two-phase voltage signals output from the differential amplifier circuit is detected, and the difference is reduced. And an error voltage detection circuit (23e) for obtaining an error compensation voltage necessary for this, and the error compensation voltage is input to at least one of the two-phase voltage signals output from the phase dividing circuit or the differential amplifier circuit. The transimpedance amplifier according to claim 1, wherein the transimpedance amplifier is superposed on at least one of the two-phase voltage signals to reduce the difference between the average potentials. A photoelectric conversion element (1) that receives an optical signal and outputs a current signal;
In an optical signal receiving device having a transimpedance amplifier (20) for receiving a current signal output from the photoelectric conversion element,
The optical signal receiving apparatus, wherein the transimpedance amplifier is the transimpedance amplifier according to claim 1.

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